Urinary System

Question 1

Functions of urinary system

Answer 1

. Clearing blood of waste metabolic products via filtration and excretion
. Balancing concentration of electrolytes in body fluids by filtration and excretion
. Reabsorption of molecules and water to maintain homeostasis
. Bp regulation via resin
. EPO production
. Conversation of vit. D3 to calcitriol
. Gluconeogenesis

Question 2

Components of urinary system

Answer 2

. 2 kidneys
. 2 ureters
. Urinary bladder
. Urethra

Question 3

Kidney gross anatomy

Answer 3

. Concave hilum faces medially
. Renal a., v. And nn. Enter and leave at hilum
. Meets w/ ureter to form renal pelvis at hilum
. Renal pelvis forms 2-3 major calyces
. Major calyces divide into 6-12 minor calyces
. Each minor calyx is where papilla of pyramid drains

Question 4

Kidney structure

Answer 4

. Cortex: outer, and juxtamedullary cortex
. Medulla: inner layer, 6-12 renal pyramids w/ base at corticomedullary junction
. Apex at hilum perforated by Ducts of Bellini forming area cribrosa
. Apex surrounded by minor calyx
. Each minor calyx collects urine droplets from area cribrosa
. Renal columns of Bertin: cortex that extend btw pyramids, part of medulla
. Pyramid w/ cortical region is renal lobe w/ renal capsule as base
. Lateral boundaries of renal lobule are renal columns

Question 5

Filtration of blood in kidneys

Answer 5

. 20% CO: entire volume of blood volume passes through every 5 minutes
. 90% blood in renal cortex, 10% medulla
. 180 L of initial filtrate is produced in 24 hrs, 1-2L is excreted as urine, rest is returned into circulation

Question 6

Kidney blood supply

Answer 6

. Renal aa.
. Segmental aa.
. Interlobar aa. Across renal columns btw pyramids
. Arcuate aa. R angle branches of interlobar aa. That arch over pyramids at corticomedullary junction
. Interlobular aa.: vertical branches of arcuate supplying renal cortex
. Afferent glomerular arterioles
. Glomerulus: tuft of anastomosing capillaries
. Efferent arterioles: drain glomerulus to 2nd capillary bed forming arterial portal system
. Peritubular capillary network or vasa recta after that

Question 7

Peritubular capillary network

Answer 7

. Distributed through cortex
. Endothelial cells w/ CT of cortex and outer medulla
. Produce most of the EPO

Question 8

Vasa recta of kidney

Answer 8

. Deep in medulla
. Descending components (arterial limb) hairpin turn and return as ascending venous limbs to corticomedullary junction
. Assoc. w/ loops of Henle and collecting ducts

Question 9

Peritubular capillaries and vasa recta drain into ____

Answer 9

Interlobular vv.
. Arcuate vv.
. Interlobar vv.
. Renal vv.

Question 10

Uriniferous tubule

Answer 10

. Nephron and collecting tubule
. Functional unit of kidney
. 600,000-1.2 million per kidney
. Forms urine
. Many nephrons drained by 1 collecting tubule
. Many collecting tubules form larger ducts in medulla
. Ducts of Bellini are largest collecting ducts

Question 11

Components of nephron

Answer 11

. Renal (Malpighian) corpuscle: glomerulus and capsule of Bowman
. Proximal convoluted tubule (PCT)
. Loop of Henle (thick (prox. Straight tubule) and thin descending, thick (distal straight tubule) and thin ascending)
. Distal convoluted tubule: Macula densa
. Collecting tubule/duct: transports filtrate to minor calyx

Question 12

Cortical nephrons

Answer 12

. 85%
. In peripheral cortex
. Short loops of Henle that reach outer medulla

Question 13

Juxtamedullary nephrons

Answer 13

. 15% 
. Near corticomedullary junction
. Long loops of Henle that extend to inner medulla 
. Important for reabsorption of water 
. Produce concentrated urine

Question 14

Bowman’s capsule

Answer 14

. Visceral layer has podocytes (1 layer of epithelial cells)
.work w/ capillary endothelial cells to facilitate initial renal filtration
. Parietal layer of SSNK continuous w/ simple cuboidal epithelium of PCT
. Urinary space: contains plasma filtrate (primary urine) btw visceral and parietal layers, continuous w/ lumen of PCT at urinary pole
. Opposite pose is where afferent articles enters and exits (vascular pole)

Question 15

Podocytes

Answer 15

. Stellate shaped
. In Bowman’s capsule
. Have primary processes and many pedicels (secondary processes)
. Pedicels interdigitate w/ neighboring pedicels and forms lit pores
. Slit pores bridges by slit diaphragms

Question 16

Slit diaphragms

Answer 16

. Specialized tight junctions made of neg. charged proteins and glycoproteins (nephrins)

Question 17

Glomerulus

Answer 17

. Tuft of type II capillaries w/o diaphragms

. Btw afferent and efferent arterioles

Question 18

Glomerular filtration barrier

Answer 18

. Thick basement membrane btw fenestrated endothelial cells and podocytes
. Made of fused basement membrane of both cells
. Separates blood from urinary space
. Restricts proteins larger then 70 kDa, blocking most plasma proteins

Question 19

Mesangium

Answer 19

. W//in glomerulus
. Replaces CT btw glomerular capillaries
. Made of mesangial cells and mesangial matrix

Question 20

Mesangial cells

Answer 20

. Pericyte-like cells in renal corpuscle
. Support glomerular capillaries
. Contract in response to changes in bp, optimize filtration rate
. Phagocytose proteins trapped in basement membrane

Question 21

Proximal convoluted tubule

Answer 21

. Fills most of cortex
. Simple cuboidal epithelium for reabsorption
. Apically have brush border
. Basally have plasma membrane w/ infolding and long mitochondria
. Laterally have tight junctions, plasma membrane interdigitations
. Active and passive reabsorption of all proteins, organic nutrients, 70% of water via tight junctions and aquaporin-1 and NaCl
. Produces calcitriol

Question 22

Loop of Henle

Answer 22

. Descending and ascending limbs
. Thick descending is continuation of PCT entering medulla, Thick ascending is continuous in cortex w/ DCT, both low cuboidal cells
. Thin descending makes hairpin turn to thin ascending, SSNK on both
. Thin descending has apuaporin-1, both ascending loops impermeable to water
. Reabsorbs 15% water, 25% NaCl, K, Ca, HCO3

Question 23

Distal convoluted tubule (DCT)

Answer 23

. Shorter than PCT (7:1 ratio)
. Simple cuboidal, short than PCT w/ no brush border
. Reabsorbs NaCl
. Impermeable to H2O until distal portion if ADH present

Question 24

Juxtaglomerular (JG) apparatus

Answer 24

. Endocrine structure that autoregulates filtration rate and bp control
. Macula densa: initial part of DCT made of columnar, densely packed cells
. JG cells: renin-producing cells of afferent glomerular arterioles and sometimes efferent arterioles
. Extraglomerular mesangial cells (lacis cells): supportive function

Question 25

How JG apparatus controls bp

Answer 25

. Low arterial pressure causes renin release from JG cells in blood . Cleavage of angiotensinogen to Angiotensin I (AI) . AI gets cleaved to AII by ACE in lung . AII vasocontricts to inc. bp and stimulates adrenal gland to release aldosterone . Aldosterone promotes Na and H2O reabsorption in DCT . Inc. blood volume, inc. bp . Return to normal bp stops renin secretion by JG cells

Question 26

Collecting duct

Answer 26

. DCTs of many nephrons joins dn form short connecting tubule leading to collecting duct . In cortical medullary rays . Many ducts form papillary duct in renal pyramid apex . Principal and intercalated cells . Simple cuboidal in shape. . Impermeable to H2O unless ADH present

Question 27

Principal cells in collecting ducts

Answer 27

``` . Majority of cells . Pale staining w/ distinct boundaries . Reabsorbs water and Na . Secrete K . ADH targets these and makes them permeable by targeting aquaporin-2 cells ```

Question 28

Intercalated cells in collecting ducts

Answer 28

. Darker staining cells | . Play role in acid-base balance by secreting H or HCO3

Question 29

Bladder structure

Answer 29

. Transitional epithelium . Inc. in thickness from ureter to urethra . Impermeable to water and salts . Dense lamina propria . Muscularis in inner longitudinal and outer circular layers . Lower third of ureter and bladder has 3rd longitudinal layer of smooth muscle

Question 30

Urethra in female

Answer 30

. 3-5 cm long . Lined by transitional epithelium that changes to SSNK . Continuous w/ labia minora

Question 31

Male urethra

Answer 31

. Prostatic lined by transitional epithelium . Membranous lined by stratified columnar and pseudostratifed columnar . Spongy, lined by stratified columnar and pseudostratified columnar w/ stratified columnar epithelium distally

Question 32

Polycystic kidney disease

Answer 32

. Hereditary . Autosomal dominant linked to mutations in primary cilia proteins . Forms large fluid-filled cysts . Causes destruction of normal kidney architecture

Question 33

Diabetic kidney disease

Answer 33

Proteinuria linked to damaged podocytes

Question 34

Glomerulonephritis

Answer 34

Inflammation of glomeruli from impairment of filtration barrier by deposition of antigen-antibody complexes . From antibodies binding directly to basement membrane

Question 35

Diuretics

Answer 35

. Drugs that inc. urine output . Common effect is inhibition of Na reabsorption by nephron . Treats hypertension and edema

Question 36

Inhibitors if renin- angiotensin system

Answer 36

. Renin, ACE and AII blockers . Hypertension treatment . Prevention of DM II